# Adafruit MCP3421 18-Bit ADC - STEMMA QT / Qwiic

**Type:** Product page · **SKU:** ADA5870 · **Brand:** [Adafruit](https://core-electronics.com.au/brands/adafruit-australia)
**Page:** https://core-electronics.com.au/adafruit-mcp3421-18-bit-adc-stemma-qt-qwiic.html ([markdown](https://core-electronics.com.au/adafruit-mcp3421-18-bit-adc-stemma-qt-qwiic.html.md))

The Adafruit MCP3421 18-Bit ADC is a simple, inexpensive, and easy to use 18-bit, 240 SPS, single-channel ADC with an I2C interface that can run up to...

## Pricing

- **Price:** $11.85 (inc GST) — $10.77 AUD, exc GST
- **Quantity discounts:** 10+ $10.45 (exc GST) · 50+ $10.24 (exc GST)

## Availability & dispatch

- In stock, ships same business day if ordered before 2PM (Australia/Sydney).
- We can dispatch 2 today, and up to 18 more in 8–12 days.

## Description

The **Adafruit MCP3421 18-Bit ADC** is a simple, inexpensive, and easy to use 18-bit, 240 SPS, single-channel ADC with an I2C interface that can run up to 3.4MHz clock rate. A perfect component whenever you need an ADC that has differential inputs, adjustable gain, and a built in precision/low-drift reference voltage.One of the trade-offs with getting 18-bit precision is that the ADC is not going to be very fast: you can configure the chip to do a faster 12-bit conversion at 240 SPS, but at 18-bits it slows down to 3.5 SPS.That's because the way a [sigma-delta ADC](https://en.wikipedia.org/wiki/Delta-sigma_modulation) works, it 'guesses' the analog voltage and uses a comparator to determine whether the input is higher or lower. Each 'guess' takes an extra step, and thushalves the throughput, so 12-bit is 240 SPS, and 14-bit is 1/4 (2-bit) slower, 60 SPS. Ditto 16-bit is 1/4 slower, 15 SPS, and finally 18-bit is 3.75 SPS.The MCP3421 is already set up for differential inputs, which means that you can read positive or negative differences between the two inputs, **as long as both signals are between 0 and 2.048V**. This means its not going to be great for reading stuff like potentiometers, where you have a single-end reading referenced to ground, and you want to read the full range from 0 to Vcc. It is great, however, for reading sensors like strain gauges, pressure sensors, or thermocouples.

[Adafruit have a ready to go Arduino library that makes usage simple](https://github.com/adafruit/Adafruit_MCP3421): select the sample rate / precision you want and one-shot or continuous mode. Then read values over I2C! This sensor has a fixed address, so [you may want to use a multiplexor](https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout) if you want to connect multiple MCP3421's on a single I2C bus.

To get you going fast, Adafruit spun up a custom-made PCB in the[ **STEMMA QT** form factor](https://core-electronics.com.au/search?q=stemma%20qt%20sensor), making it easy to interface with. The [STEMMA QT connectors](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma-qt) on either side are compatible with the [SparkFun Qwiic](https://core-electronics.com.au/catalogsearch/result/?q=qwiic) I2C connectors. This allows you to make solderless connections between your development board and the MCP or to chain it with a wide range of other sensors and accessories using a [**compatible cable**](https://core-electronics.com.au/search?q=stemma%20qt%20cable).

[QT Cable is not included, we have a variety listed on our site](https://core-electronics.com.au/search?q=stemma+qt+cable).

Comes with a bit of 0.1" standard header in case you want to use it with a breadboard or perfboard. Four mounting holes for easy attachment.

## Technical Details

- 18-bit ΔΣ ADC
- Differential Input Operation
- Self Calibration of Internal Offset and Gain Per Each Conversion
- On-Board Voltage Reference: 
    - Accuracy: 2.048V ± 0.05%
    - Drift: 15 ppm/°C
- On-Board Programmable Gain Amplifier (PGA): 
    - Gains of 1,2, 4 or 8
- On-Board Oscillator
- INL: 10 ppm of FSR (FSR = 4.096V/PGA)
- Programmable Data Rate Options: 
    - 3.75 SPS (18 bits)
    - 15 SPS (16 bits)
    - 60 SPS (14 bits)
    - 240 SPS (12 bits)
- One-Shot or Continuous Conversion Options
 
Product Dimensions: 25.4mm x 17.8mm x 12.3mm

Product Weight: 3.0g

## Images

- [Product image 1](https://core-electronics.com.au/media/catalog/product/A/D/ADA5870-1.jpg)